Speaker: Claudia Scarlata, SSC, Caltech
Abstract: Extended Lyman alpha nebulae: hot or cold?
The mechanism powering Lyman alpha emission in extended Lyman alpha
nebulae discovered at high redshifts is still elusive. These nebulae
are similar to those observed around high redshift radio galaxies, but
they are not associated with either radio or Xray sources. Various
mechanisms have been proposed to power the emission, including
photoionization by a dust enshrouded AGN, interaction between the IGM
and the super winds produced in a starburst, and cooling radiation from
gas falling in a galaxy potential well. I will present recent results
from a study of an extended Lyman-alpha nebula at z=2.4, associated with
two dusty sources at the same redshift.
Using a combination of rest-frame UV and mid-IR spectroscopy and imaging
to constrain the source of energy, I find that the mechanism that best
reproduces all the observed properties of this peculiar object is gas
cooling through cold filaments.
I will also present some related results on the role that the dust
geometry has on the escape of the Lyman alpha photons. Using a sample of
z~0.3 Lyman alpha emitters I will show that Lyman alpha photons escape
through clean line of sights within the galaxy, following similar paths
traveled by Balmer and continuum photons.